Field Chronology

1978. Partial field season.

July 23. Bob Makela and I stop at the Brandvolds' rock shop in Bynum, Montana, where we are shown some small bones that turn out to be very rare fossils of baby dinosaurs. Late July, early August. Bob and I collect from the surface of the site on the Peebles ranch and dig up the first nest of baby dinosaurs ever found, as well as an adult skull discovered by the Brandvolds. The state of the baby bones indicates that these young stayed in the nest for some time and were cared for by adults. We name the new dinosaur Maiasaura—Good Mother Lizard. Late summer. Amy Luthin finds the first sign of a second nest.

1979. First full year of digging. We set up camp on A. B. Guthrie's land on the Teton River.

June, early July. As we find more maiasaur nests, it begins to seem that we have discovered a colonial nesting ground of maiasaurs. July 2. We start to work on a new site that the Brandvolds are working, a jumbled collection of bones of adult and young dinosaurs. This is the very first hint of what we will eventually realize is a bone bed containing fossil remnants of a herd of 10,000 maiasaurs. July 12. Fran Tannenbaum discovers Egg Mountain, where we find one egg after another. In the years to come, this site will yield several nesting grounds of a small creature that is a variety of hypsilophodontid dinosaur.

1980. We set up camp on the Peebles ranch in the heart of the Willow Creek anticline, where we will stay for the duration of the dig.

June. We find another apparent maiasaur nest in what is now clearly a preserved colonial nesting ground. July, August. We work on the Brandvold site and similar deposits of adult and juvenile bones without yet realizing they are connected. We also continue to explore the surface of Egg Mountain, finding more egg clutches and growing more confident that there are other nesting grounds preserved there.

1981. Excavation of the first maiasaur nesting ground is complete. A total of eight nests have been uncovered on one fossil soil surface, indicating that maiasaurs gathered here to lay eggs. The same appears to be true for egg clutches on Egg Mountain laid by the hypsilophodontid that we will eventually name Orodromeus makelai. Together, these finds represent the first evidence of colonial nesting in dinosaurs.

June. Wayne Cancro, arriving early, is forced to move his tent because fossils are poking into his back. We begin to work this site, in camp, and call it Camposaur. It is very similar to the Brandvold site in the kinds of bones and their condition. Throughout the summer we find indications of similar deposits. By the end of the summer, rough stratigraphic measurements will show they are all part of one big bone bed. It seems that an entire herd of maiasaurs was destroyed all at once by some natural disaster. July, August. We continue to collect from the surface of Egg Mountain but cannot get very deep because of the hardness of the rock.

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